Electricity: measuring and testing – Magnetic – Displacement
Patent
1993-09-03
1995-08-15
O'Shea, Sandra L.
Electricity: measuring and testing
Magnetic
Displacement
324251, 324174, 32420725, 327511, 307116, G01R 3306, G01B 714, H03K 522
Patent
active
054422833
ABSTRACT:
The Hall sensor circuit includes a Hall element that is preferably followed by a Hall-voltage amplifier, and a pole end of a magnet is preferably fixed adjacent to the Hall element. The amplifier output is connected directly to one of a pair of differential inputs of a Schmitt trigger circuit and is also connected, via a single or a dual-polarity track and hold circuit, to the other of the differential Schmitt inputs. The dual-polarity track and hold circuit causes the voltage across a capacitor to track positive and negative Hall voltage slopes, and to hold the positive-going peaks and negative-going peaks of the Hall voltage presented to the fore-mentioned other Schmitt input so that when the difference voltage between the Hall voltage and the held voltage of the capacitor exceeds a positive or negative threshold of the Schmitt circuit, the Schmitt circuit output changes binary state indicating the approaching edge or the receding edge of a ferrous-gear tooth. The dual-polarity track and hold circuit is made up of two complementary plus and a minus peak detector circuits, each including a bipolar transistor having an emitter connected to the voltage-holding capacitor, an operational amplifier with an output connected to the base of the transistor, the amplifier having a negative input connected to the transistor emitter and a positive input serving as the input of the each Hall voltage tracking and holding circuit.
REFERENCES:
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patent: 5241270 (1993-08-01), Ng
Bilotti Alberto
Vig Ravi
Yabusaki Hitoshi
Allegro Microsystems Inc.
O'Shea Sandra L.
Patidar Jay M.
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